The present Internet Protocol version 4 (IPv4) has many disadvantages in such aspects as address capacity, peer-to-peer IP connection, quality of service, network security, and mobility. The huge address capacity as well as various potential advantages and functions provided by IPv6 makes it an important foundation for the next generation network. Compared with IPv4, an important advantage of IPv6 is the real mobility. Mobile Internet Protocol version 6 (Mobile IPv6) could provide more flexibility for new functions and services. Through simple extensions, Mobile IPv6 could satisfy the demands of a large number of mobile devices, and provide a globally unique IP address for each mobile terminal operating in the Internet. Thus, the global problem of mobility related to the network and the accessing technology could be solved.
Although IPv6 network has more advantages than IPv4, they will coexist for a long time. At present, almost every network and access device supports IPv4, thus it is impractical to switch from IPv4 to IPv6 quickly. In many cases of such coexistence, the devices in an IPv4 network would have the need for IPv6 services, so do the devices in an IPv6 network different from that of their communication counterparts, thus leading to the issue of how to provide IPv6 services for such devices.
In order to provide devices with IPv6 services when an IPv4 network and an IPv6 network coexist, one present solution is upgrading the present network to a network supporting the IPv4 & IPv6 dual protocol stacks. According to this solution, all the 3′ layer network devices such as routers and switches, as well as user terminals in the network are upgraded to support IPv6&IPv4 dual protocol stacks. Each device has an IPv4 address and an IPv6 address. Therefore, devices could communicate with the IPv4 protocol stack when allowed; and the devices could also use the IPv6 protocol stack to communicate when the IPv4 protocol stack could not guarantee a normal communication due to the private address problem as a result of the NAT devices existing in the network.
In the prior art, devices could also access the IPv6 network for some certain services in a standard tunnel mode, wherein the tunnel may include an Intra-site Automatic Tunnel Addressing Protocol (ISATAP) tunnel, a 6 to 4 tunnel, a configured tunnel, a Tunneling IPv6 over UDP through NATs (TEREDO) tunnel. When the device accesses the IPv6 network through a standard tunnel, an IPv6 address associated to the tunnel could be acquired from a tunnel gateway through which the device could make communications to receive IPv6 services.